#ifndef __Skygen_ImprovedPerlinNoise_h__
#define __Skygen_ImprovedPerlinNoise_h__

namespace Orca {

	template<typename real>
	class TImprovedPerlinNoise {

	public:
		TImprovedPerlinNoise() {

			int permutation[] = { 
				151,160,137,91,90,15,
				131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,
				21,10,23,190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,
				35,11,32,57,177,33,88,237,149,56,87,174,20,125,136,171,168, 68,175,
				74,165,71,134,139,48,27,166,77,146,158,231,83,111,229,122,60,211,133,
				230,220,105,92,41,55,46,245,40,244,102,143,54, 65,25,63,161, 1,216,
				80,73,209,76,132,187,208, 89,18,169,200,196,135,130,116,188,159,86,
				164,100,109,198,173,186, 3,64,52,217,226,250,124,123,5,202,38,147,
				118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,223,
				183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,
				172,9,129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,
				218,246,97,228,251,34,242,193,238,210,144,12,191,179,162,241, 81,51,
				145,235,249,14,239,107,49,192,214,31,181,199,106,157,184, 84,204,176,
				115,121,50,45,127, 4,150,254,138,236,205,93,222,114,67,29,24,72,243,
				141,128,195,78,66,215,61,156,180
				};

			for(int i = 0; i < 256; i++) 
				p[256+i] = p[i] = permutation[i]; 
		}

		real pnoise(real x, real y, real z) {

			int   X = (int)floor(x) & 255,										// FIND UNIT CUBE THAT
				  Y = (int)floor(y) & 255,										// CONTAINS POINT.
				  Z = (int)floor(z) & 255;

			x -= floor(x);														// FIND RELATIVE X,Y,Z
			y -= floor(y);														// OF POINT IN CUBE.
			z -= floor(z);

			real u = _fade(x),													// COMPUTE FADE CURVES
				 v = _fade(y),													// FOR EACH OF X,Y,Z.
				 w = _fade(z);

			int  A	= p[X]+Y, 
				 AA = p[A]+Z, 
				 AB = p[A+1]+Z,													// HASH COORDINATES OF
				 B	= p[X+1]+Y, 
				 BA = p[B]+Z, 
				 BB = p[B+1]+Z;													// THE 8 CUBE CORNERS

			return _lerp(
						w,
						_lerp(
							v,
							_lerp(
								u,
								grad(p[AA  ], x, y, z),							// AND ADD
								grad(p[BA  ], x-1, y, z)),						// BLENDED
							_lerp(
								u,
								grad(p[AB  ], x, y-1, z),						// RESULTS
								grad(p[BB  ], x-1, y-1, z))),					// FROM  8
						_lerp(
							v,
							_lerp(
								u,
								grad(p[AA+1], x, y, z-1 ),						// CORNERS
								grad(p[BA+1], x-1, y, z-1)),					// OF CUBE
							_lerp(
								u,
								grad(p[AB+1], x, y-1, z-1),
								grad(p[BB+1], x-1, y-1, z-1))));
		}
		
	private:
		int p[512];
		
		real _fade(real t) {
			return t * t * t * (t * (t * 6 - 15) + 10);
		}

		real _lerp(real t, real a, real b) {
			return a + t * (b - a);
		}

		real grad(int hash, real x, real y, real z) {

			int   h = hash & 15;												// CONVERT LO 4 BITS OF HASH CODE
			real  u = h < 8 ? x : y,											// INTO 12 GRADIENT DIRECTIONS.
					v = h < 4 ? y : h==12||h==14 ? x : z;

			return 
				((h&1) == 0 ? u : -u) + 
				((h&2) == 0 ? v : -v);
		}
};
}

#endif	// __Skygen_ImprovedPerlinNoise_h__